Exterior cloaking with active sources in two dimensional acoustics

We cloak a region from a known incident wave by surrounding the region with three or more devices that cancel out the field in the cloaked region without significantly radiating waves. Since very little waves reach scatterers within the cloaked region, the scattered field is small and the scatterers are for all practical purposes undetectable. The devices are multipolar point sources that can be determined from Green's formula and an addition theorem for Hankel functions. The cloaking devices are exterior to the cloaked region.

Research Highlights
► Multipolar sources cancel a field in a region without radiating in the far field.
► An object inside this region is for all practical purposes invisible.
► The cloaked region is connected with the exterior.
► The sources come from Green's formula for the Helmholtz equation.
► Our method compares favorably to earlier designs based on optimization.